Method and apparatus for performing inter-frequency and/or inter-radio access technology measurements

ABSTRACT

Techniques for performing inter-frequency and/or inter-radio access technology (RAT) measurements are disclosed. A multi-receiver wireless transmit/receive unit (WTRU) may receive downlink transmissions via a plurality of downlink carriers simultaneously. The WTRU may perform inter-frequency and/or inter-RAT measurements using an inactive receiver without measurement gaps if at least one receiver is inactive. If the WTRU receives a measurement order on a disabled carrier, the WTRU may perform measurements on the disabled carrier without measurement gaps using an inactive receiver while maintaining a status of the disabled carrier as disabled. The WTRU may perform the measurements autonomously if a trigger condition is met and at least one receiver is inactive. If all receivers are active, the WTRU may perform the measurements using measurement gaps, that may be configured on a downlink carrier, or alternatively, on an unpaired downlink carrier, or alternatively, on a subset of associated downlink uplink carrier pairs.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/896,414 filed Oct. 1, 2010, which claims the benefit of U.S.Provisional Application Ser. No. 61/247,628 filed Oct. 1, 2009, thecontents of which are hereby incorporated by reference herein.

BACKGROUND

Dual-cell high speed downlink packet access (HSDPA) has been introducedin the third generation partnership project (3GPP) Release 8 as part ofthe continuing evolution of high speed packet access (HSPA) systems.This feature allows simultaneous downlink (DL) transmission andreception on two adjacent carriers on the high-speed channels. As partof 3GPP Release 9, the feature was extended to support DL transmissionand reception on non-adjacent DL carriers, (e.g., carriers in differentfrequency bands). The ability to support simultaneous reception onnon-adjacent carriers significantly impacts the radio frequency (RF)design of a wireless transmit/receive unit (WTRU) including separate RFreceivers.

In order to support inter-frequency and inter-radio access technology(RAT) handovers, a WTRU performs measurements on other frequenciesand/or other RATs and report the measurements to the radio accessnetwork. In case where a WTRU is equipped with a single RF receiver, theWTRU performs the inter-frequency and/or inter-RAT measurements duringthe measurement gaps. During the measurement gaps, a downlinktransmission to the WTRU is interrupted, and the WTRU is allowed to tuneits RF receiver to other frequencies and/or RATs to perform theinter-frequency and/or inter-RAT measurements. In 3GPP universal mobiletelecommunication systems (UMTS) wireless communications systems, thesemeasurements gaps are referred to as compressed mode (CM) gaps. Inaccordance with the current 3GPP UMTS specification, both the DLreception and the UL transmission are interrupted during the CM gaps,which causes a degradation of service.

SUMMARY

A method and apparatus for performing inter-frequency and/or inter-radioaccess technology (RAT) measurements are disclosed. A multi-receiverwireless transmit/receive unit (WTRU) may receive downlink transmissionsvia a plurality of downlink carriers simultaneously. The WTRU mayperform inter-frequency and/or inter-RAT measurements using an inactivereceiver without measurement gaps if at least one receiver is inactive.If the WTRU receives a measurement order on a disabled carrier, the WTRUmay perform measurements on the disabled carrier without measurementgaps using an inactive receiver while maintaining a status of thedisabled carrier as disabled at a physical layer. The WTRU may performthe performing the inter-frequency and/or inter-RAT measurementsautonomously on a condition that the trigger condition is met and atleast one receiver is inactive.

If all receivers are active, the WTRU may perform the measurements usingmeasurement gaps, wherein the measurement gaps may be configured on adownlink carrier and not on an uplink carrier, or alternatively, on anunpaired downlink carrier and not on a paired downlink carrier, oralternatively, on a subset of associated downlink uplink carrier pairs.

The WTRU may send a proximity indication on a condition that the WTRU isnear a detected home Node-B (HNB)/evolved HNB (eHNB) cell whose identityis in a list, and perform inter-frequency and/or inter-RAT measurementson a frequency carrier or an RAT of the detected HNB/eHNB cell whileconfiguring with at least one receiver inactive and/or autonomous gaps.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding may be had from the following description,given by way of example in conjunction with the accompanying drawingswherein:

FIG. 1A is a system diagram of an example communications system in whichone or more disclosed embodiments may be implemented;

FIG. 1B is a system diagram of an example wireless transmit/receive unit(WTRU) that may be used within the communications system illustrated inFIG. 1A;

FIG. 1C is a system diagram of an example radio access network and anexample core network that may be used within the communications systemillustrated in FIG. 1A;

FIG. 2 shows an example downlink (DL) and uplink (UL) carrierconfiguration with measurement gaps on the DL carrier in accordance withone embodiment;

FIG. 3 shows an example DL and UL carrier configuration with measurementgaps on the DL carrier in accordance with another embodiment;

FIG. 4 shows an example DL and UL carrier configuration with measurementgaps on the DL carrier in accordance with an alternative embodiment;

FIGS. 5A and 5B is a flow diagram of an example process for autonomousinter-frequency and/or inter-RAT measurements in accordance with oneembodiment; and

FIGS. 6A and 6B is a flow diagram of an example process for performinginter-frequency and/or inter-RAT measurements in accordance with anotherembodiment.

DETAILED DESCRIPTION

FIG. 1A is a diagram of an example communications system 100 in whichone or more disclosed embodiments may be implemented. The communicationssystem 100 may be a multiple access system that provides content, suchas voice, data, video, messaging, broadcast, etc., to multiple wirelessusers. The communications system 100 may enable multiple wireless usersto access such content through the sharing of system resources,including wireless bandwidth. For example, the communications systems100 may employ one or more channel access methods, such as code divisionmultiple access (CDMA), time division multiple access (TDMA), frequencydivision multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrierFDMA (SC-FDMA), and the like.

As shown in FIG. 1A, the communications system 100 may include wirelesstransmit/receive units (WTRUs) 102 a, 102 b, 102 c, 102 d, a radioaccess network (RAN) 104, a core network 106, a public switchedtelephone network (PSTN) 108, the Internet 110, and other networks 112,though it will be appreciated that the disclosed embodiments contemplateany number of WTRUs, base stations, networks, and/or network elements.Each of the WTRUs 102 a, 102 b, 102 c, 102 d may be any type of deviceconfigured to operate and/or communicate in a wireless environment. Byway of example, the WTRUs 102 a, 102 b, 102 c, 102 d may be configuredto transmit and/or receive wireless signals and may include userequipment (UE), a mobile station, a fixed or mobile subscriber unit, apager, a cellular telephone, a personal digital assistant (PDA), asmartphone, a laptop, a netbook, a personal computer, a wireless sensor,consumer electronics, and the like.

The communications systems 100 may also include a base station 114 a anda base station 114 b. Each of the base stations 114 a, 114 b may be anytype of device configured to wirelessly interface with at least one ofthe WTRUs 102 a, 102 b, 102 c, 102 d to facilitate access to one or morecommunication networks, such as the core network 106, the Internet 110,and/or the networks 112. By way of example, the base stations 114 a, 114b may be a base transceiver station (BTS), a Node-B, an eNode B, a HomeNode B, a Home eNode B, a site controller, an access point (AP), awireless router, and the like. While the base stations 114 a, 114 b areeach depicted as a single element, it will be appreciated that the basestations 114 a, 114 b may include any number of interconnected basestations and/or network elements.

The base station 114 a may be part of the RAN 104, which may alsoinclude other base stations and/or network elements (not shown), such asa base station controller (BSC), a radio network controller (RNC), relaynodes, etc. The base station 114 a and/or the base station 114 b may beconfigured to transmit and/or receive wireless signals within aparticular geographic region, which may be referred to as a cell (notshown). The cell may further be divided into cell sectors. For example,the cell associated with the base station 114 a may be divided intothree sectors. Thus, in one embodiment, the base station 114 a mayinclude three transceivers, i.e., one for each sector of the cell. Inanother embodiment, the base station 114 a may employ multiple-inputmultiple output (MIMO) technology and, therefore, may utilize multipletransceivers for each sector of the cell.

The base stations 114 a, 114 b may communicate with one or more of theWTRUs 102 a, 102 b, 102 c, 102 d over an air interface 116, which may beany suitable wireless communication link (e.g., radio frequency (RF),microwave, infrared (IR), ultraviolet (UV), visible light, etc.). Theair interface 116 may be established using any suitable radio accesstechnology (RAT).

More specifically, as noted above, the communications system 100 may bea multiple access system and may employ one or more channel accessschemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. Forexample, the base station 114 a in the RAN 104 and the WTRUs 102 a, 102b, 102 c may implement a radio technology such as Universal MobileTelecommunications System (UMTS) Terrestrial Radio Access (UTRA), whichmay establish the air interface 116 using wideband CDMA (WCDMA). WCDMAmay include communication protocols such as High-Speed Packet Access(HSPA) and/or Evolved HSPA (HSPA+). HSPA may include High-Speed DownlinkPacket Access (HSDPA) and/or High-Speed Uplink Packet Access (HSUPA).

In another embodiment, the base station 114 a and the WTRUs 102 a, 102b, 102 c may implement a radio technology such as Evolved UMTSTerrestrial Radio Access (E-UTRA), which may establish the air interface116 using Long Term Evolution (LTE) and/or LTE-Advanced (LTE-A).

In other embodiments, the base station 114 a and the WTRUs 102 a, 102 b,102 c may implement radio technologies such as IEEE 802.16 (i.e.,Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000,CDMA2000 1X, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), InterimStandard 95 (IS-95), Interim Standard 856 (IS-856), Global System forMobile communications (GSM), Enhanced Data rates for GSM Evolution(EDGE), GSM EDGE (GERAN), and the like.

The base station 114 b in FIG. 1A may be a wireless router, Home Node B,Home eNode B, or access point, for example, and may utilize any suitableRAT for facilitating wireless connectivity in a localized area, such asa place of business, a home, a vehicle, a campus, and the like. In oneembodiment, the base station 114 b and the WTRUs 102 c, 102 d mayimplement a radio technology such as IEEE 802.11 to establish a wirelesslocal area network (WLAN). In another embodiment, the base station 114 band the WTRUs 102 c, 102 d may implement a radio technology such as IEEE802.15 to establish a wireless personal area network (WPAN). In yetanother embodiment, the base station 114 b and the WTRUs 102 c, 102 dmay utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE,LTE-A, etc.) to establish a picocell or femtocell. As shown in FIG. 1A,the base station 114 b may have a direct connection to the Internet 110.Thus, the base station 114 b may not be required to access the Internet110 via the core network 106.

The RAN 104 may be in communication with the core network 106, which maybe any type of network configured to provide voice, data, applications,and/or voice over internet protocol (VoIP) services to one or more ofthe WTRUs 102 a, 102 b, 102 c, 102 d. For example, the core network 106may provide call control, billing services, mobile location-basedservices, pre-paid calling, Internet connectivity, video distribution,etc., and/or perform high-level security functions, such as userauthentication. Although not shown in FIG. 1A, it will be appreciatedthat the RAN 104 and/or the core network 106 may be in direct orindirect communication with other RANs that employ the same RAT as theRAN 104 or a different RAT. For example, in addition to being connectedto the RAN 104, which may be utilizing an E-UTRA radio technology, thecore network 106 may also be in communication with another RAN (notshown) employing a GSM radio technology.

The core network 106 may also serve as a gateway for the WTRUs 102 a,102 b, 102 c, 102 d to access the PSTN 108, the Internet 110, and/orother networks 112. The PSTN 108 may include circuit-switched telephonenetworks that provide plain old telephone service (POTS). The Internet110 may include a global system of interconnected computer networks anddevices that use common communication protocols, such as thetransmission control protocol (TCP), user datagram protocol (UDP) andthe internet protocol (IP) in the TCP/IP internet protocol suite. Thenetworks 112 may include wired or wireless communications networks ownedand/or operated by other service providers. For example, the networks112 may include another core network connected to one or more RANs,which may employ the same RAT as the RAN 104 or a different RAT.

Some or all of the WTRUs 102 a, 102 b, 102 c, 102 d in thecommunications system 100 may include multi-mode capabilities, i.e., theWTRUs 102 a, 102 b, 102 c, 102 d may include multiple transceivers forcommunicating with different wireless networks over different wirelesslinks. For example, the WTRU 102 c shown in FIG. 1A may be configured tocommunicate with the base station 114 a, which may employ acellular-based radio technology, and with the base station 114 b, whichmay employ an IEEE 802 radio technology.

FIG. 1B is a system diagram of an example WTRU 102. As shown in FIG. 1B,the WTRU 102 may include a processor 118, a transceiver unit 120, atransmit/receive element 122, a speaker/microphone 124, a keypad 126, adisplay/touchpad 128, non-removable memory 106, removable memory 132, apower source 134, a global positioning system (GPS) chipset 136, andother peripherals 138. It will be appreciated that the WTRU 102 mayinclude any sub-combination of the foregoing elements while remainingconsistent with an embodiment.

The processor 118 may be a general purpose processor, a special purposeprocessor, a conventional processor, a digital signal processor (DSP), aplurality of microprocessors, one or more microprocessors in associationwith a DSP core, a controller, a microcontroller, Application SpecificIntegrated Circuits (ASICs), Field Programmable Gate Array (FPGAs)circuits, any other type of integrated circuit (IC), a state machine,and the like. The processor 118 may perform signal coding, dataprocessing, power control, input/output processing, and/or any otherfunctionality that enables the WTRU 102 to operate in a wirelessenvironment. The processor 118 may be coupled to the transceiver 120,which may be coupled to the transmit/receive element 122. While FIG. 1Bdepicts the processor 118 and the transceiver 120 as separatecomponents, it will be appreciated that the processor 118 and thetransceiver 120 may be integrated together in an electronic package orchip.

The transmit/receive element 122 may be configured to transmit signalsto, or receive signals from, a base station (e.g., the base station 114a) over the air interface 116. For example, in one embodiment, thetransmit/receive element 122 may be an antenna configured to transmitand/or receive RF signals. In another embodiment, the transmit/receiveelement 122 may be an emitter/detector configured to transmit and/orreceive IR, UV, or visible light signals, for example. In yet anotherembodiment, the transmit/receive element 122 may be configured totransmit and receive both RF and light signals. It will be appreciatedthat the transmit/receive element 122 may be configured to transmitand/or receive any combination of wireless signals.

In addition, although the transmit/receive element 122 is depicted inFIG. 1B as a single element, the WTRU 102 may include any number oftransmit/receive elements 122. More specifically, the WTRU 102 mayemploy MIMO technology. Thus, in one embodiment, the WTRU 102 mayinclude two or more transmit/receive elements 122 (e.g., multipleantennas) for transmitting and receiving wireless signals over the airinterface 116.

The transceiver 120 may be configured to modulate the signals that areto be transmitted by the transmit/receive element 122 and to demodulatethe signals that are received by the transmit/receive element 122. Asnoted above, the WTRU 102 may have multi-mode capabilities. Thus, thetransceiver 120 may include multiple transceivers for enabling the WTRU102 to communicate via multiple RATs, such as UTRA and IEEE 802.11, forexample. For example, the transceiver 120 may at least one RFtransmitter and a plurality of RF receivers so that the WTRU 102 mayreceive on two or more adjacent or non-adjacent frequency carrierssimultaneously. This multi-receiver capability may be realized byimplementing multiple independent RF receivers, or by using a singleadvanced RF receiver which is capable of processing multiple carriers,or by any other means.

The processor 118 of the WTRU 102 may be coupled to, and may receiveuser input data from, the speaker/microphone 124, the keypad 126, and/orthe display/touchpad 128 (e.g., a liquid crystal display (LCD) displayunit or organic light-emitting diode (OLED) display unit). The processor118 may also output user data to the speaker/microphone 124, the keypad126, and/or the display/touchpad 128. In addition, the processor 118 mayaccess information from, and store data in, any type of suitable memory,such as the non-removable memory 106 and/or the removable memory 132.The non-removable memory 106 may include random-access memory (RAM),read-only memory (ROM), a hard disk, or any other type of memory storagedevice. The removable memory 132 may include a subscriber identitymodule (SIM) card, a memory stick, a secure digital (SD) memory card,and the like. In other embodiments, the processor 118 may accessinformation from, and store data in, memory that is not physicallylocated on the WTRU 102, such as on a server or a home computer (notshown).

The processor 118 may receive power from the power source 134, and maybe configured to distribute and/or control the power to the othercomponents in the WTRU 102. The power source 134 may be any suitabledevice for powering the WTRU 102. For example, the power source 134 mayinclude one or more dry cell batteries (e.g., nickel-cadmium (NiCd),nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion),etc.), solar cells, fuel cells, and the like.

The processor 118 may also be coupled to the GPS chipset 136, which maybe configured to provide location information (e.g., longitude andlatitude) regarding the current location of the WTRU 102. In additionto, or in lieu of, the information from the GPS chipset 136, the WTRU102 may receive location information over the air interface 116 from abase station (e.g., base stations 114 a, 114 b) and/or determine itslocation based on the timing of the signals being received from two ormore nearby base stations. It will be appreciated that the WTRU 102 mayacquire location information by way of any suitablelocation-determination method while remaining consistent with anembodiment.

The processor 118 may further be coupled to other peripherals 138, whichmay include one or more software and/or hardware modules that provideadditional features, functionality and/or wired or wirelessconnectivity. For example, the peripherals 138 may include anaccelerometer, an e-compass, a satellite transceiver, a digital camera(for photographs or video), a universal serial bus (USB) port, avibration device, a television transceiver, a hands free headset, aBluetooth® module, a frequency modulated (FM) radio unit, a digitalmusic player, a media player, a video game player module, an Internetbrowser, and the like.

FIG. 1C is a system diagram of the RAN 104 and the core network 106according to an embodiment. As noted above, the RAN 104 may employ aUTRA radio technology to communicate with the WTRUs 102 a, 102 b, 102 cover the air interface 116. The RAN 104 may also be in communicationwith the core network 106. As shown in FIG. 1C, the RAN 104 may includeNode-Bs 140 a, 140 b, 140 c, which may each include one or moretransceivers for communicating with the WTRUs 102 a, 102 b, 102 c overthe air interface 116. The Node-Bs 140 a, 140 b, 140 c may each beassociated with a particular cell (not shown) within the RAN 104. TheRAN 104 may also include RNCs 142 a, 142 b. It will be appreciated thatthe RAN 104 may include any number of Node-Bs and RNCs while remainingconsistent with an embodiment.

As shown in FIG. 1C, the Node-Bs 140 a, 140 b may be in communicationwith the RNC 142 a. Additionally, the Node-B 140 c may be incommunication with the RNC 142 b. The Node-Bs 140 a, 140 b, 140 c maycommunicate with the respective RNCs 142 a, 142 b via an Iub interface.The RNCs 142 a, 142 b may be in communication with one another via anIur interface. Each of the RNCs 142 a, 142 b may be configured tocontrol the respective Node-Bs 140 a, 140 b, 140 c to which it isconnected. In addition, each of the RNCs 142 a, 142 b may be configuredto carry out or support other functionality, such as outer loop powercontrol, load control, admission control, packet scheduling, handovercontrol, macrodiversity, security functions, data encryption, and thelike.

The core network 106 shown in FIG. 1C may include a media gateway (MGW)144, a mobile switching center (MSC) 146, a serving GPRS support node(SGSN) 148, and/or a gateway GPRS support node (GGSN) 150. While each ofthe foregoing elements are depicted as part of the core network 106, itwill be appreciated that any one of these elements may be owned and/oroperated by an entity other than the core network operator.

The RNC 142 a in the RAN 104 may be connected to the MSC 146 in the corenetwork 106 via an IuCS interface. The MSC 146 may be connected to theMGW 144. The MSC 146 and the MGW 144 may provide the WTRUs 102 a, 102 b,102 c with access to circuit-switched networks, such as the PSTN 108, tofacilitate communications between the WTRUs 102 a, 102 b, 102 c andtraditional land-line communications devices.

The RNC 142 a in the RAN 104 may also be connected to the SGSN 148 inthe core network 106 via an IuPS interface. The SGSN 148 may beconnected to the GGSN 150. The SGSN 148 and the GGSN 150 may provide theWTRUs 102 a, 102 b, 102 c with access to packet-switched networks, suchas the Internet 110, to facilitate communications between and the WTRUs102 a, 102 b, 102 c and IP-enabled devices.

As noted above, the core network 106 may also be connected to thenetworks 112, which may include other wired or wireless networks thatare owned and/or operated by other service providers.

Hereafter, the embodiments will be described in the context of 3GPP UMTSwireless communication systems. However, it should be noted that theembodiments are applicable to any wireless technologies whereinter-frequency and/or inter-RAT measurements are performed to supportmobility including, but not limited to, long term evolution (LTE),LTE-Advanced (LTE-A), WiMax, and any other wireless communicationsystems.

Hereafter, the terminology “multi-receiver WTRU” will be used todescribe a WTRU that is capable of reception on two or more adjacent ornon-adjacent frequency carriers simultaneously. On the transmit side,the multi-receiver WTRU may have a capability of transmission either ona single frequency carrier or on two or more adjacent or non-adjacentfrequency carriers simultaneously. This multi-receiver capability may berealized by implementing multiple independent RF receivers, or by usinga single advanced RF receiver which is capable of processing multiplecarriers, or by any other means. Hereafter, the terminology “receiver”will be used to describe a capability of the multi-receiver WTRU forreceiving and processing a single carrier either by an independent RFreceiver or by a single advanced receiver.

Embodiments for performing inter-frequency and/or inter-RAT measurementswhere all receivers of the multi-receiver WTRU are active are explainedhereafter. One example of this case is when a dual-band dual-cell HSDPAcapable WTRU with two receivers is configured to receive on two downlinkcarriers that are either adjacent or non-adjacent.

In accordance with one embodiment, if at least one DL carrier isconfigured without an associated UL carrier, the measurement gaps,(e.g., compressed mode (CM) gaps), may be configured on the DL, withoutany gap or interruption on the UL. FIG. 2 shows an example DL and ULcarrier configuration with measurement gaps on the DL carrier inaccordance with this embodiment. In this example, a WTRU is configuredwith two DL carriers and one UL carrier. The WTRU includes two receiversand both receivers are active to process the two DL carriers. The firstDL carrier is associated with the single UL carrier, and the second DLcarrier is an unpaired carrier. As shown in FIG. 2, the measurement gapsmay be configured on the unpaired DL carrier, without any measurementgaps on the UL carrier. Alternatively, the measurement gaps may beconfigured both on the paired DL carrier and its associated UL carrier,but not on the unpaired DL. Additionally, it is possible thatmeasurements gaps may be configured on all of the DL and UL carriers orany allowable subset of carriers. During the DL measurement gaps, theWTRU may perform inter-frequency and/or inter-RAT measurements and theNode-B may not schedule any transmissions to the WTRU on the DLcarrier(s) on which the measurement gaps are configured.

In accordance with another embodiment, if a measurement gap isconfigured for a DL carrier that has an associated UL carrier, themeasurement gaps may be applied to both the UL and DL carriers, (e.g.,CM gaps are applied to the UL carrier as well), but the measurement gapsmay not be applied to all carriers, (i.e., on a subset of associateddownlink uplink carrier pairs).

FIG. 3 shows an example DL and UL carrier configuration with measurementgaps on the DL carrier in accordance with this embodiment. In thisexample, a WTRU is configured with two DL carriers and two UL carriers.The WTRU includes two receivers and both receivers are active to processthe two DL carriers. The first DL carrier is associated with the firstUL carrier, and the second DL carrier is associated with the second ULcarrier. The measurement gaps are configured on the second DL carrier,and the WTRU may not transmit during the measurement gaps on theassociated UL carrier, (i.e., the second UL carrier in this example).

During the measurement gaps, a WTRU may perform inter-frequency and/orinter-RAT measurements. The Node-B may not schedule any transmissions tothe WTRU on the carrier(s) on which the measurement gaps are configured.The WTRU may apply the conventional CM mode procedures to the associatedUL carrier and not transmit during the measurement gaps.

A combination of the above two embodiments may be implemented in casewhere multiple DL carriers are configured for measurement gaps and atleast one DL carrier has an associated UL carrier and at least one DLcarrier does not. FIG. 4 shows an example DL and UL carrierconfiguration with measurement gaps on the DL carrier in accordance withan alternative embodiment. In this example, a WTRU is configured withthree DL carriers and two UL carriers. The WTRU includes three receiversand all receivers are active to process the three DL carriers. The firstDL carrier is associated with the first UL carrier, the second DLcarrier is associated with the second UL carrier, and the third DLcarrier is unpaired. The measurement gaps are configured on the secondand third DL carriers, and the WTRU may not transmit during themeasurement gaps on the second UL carrier, which is assocated with thesecond DL carrier.

For all of the embodiments above, the WTRU may determine the carrier(s)configured for measurement gaps based on an explicit or implicitindication from the network. The indication may be received via a higherlayer configuration message for configuring the measurement gaps, (e.g.,radio resource control (RRC) message that carries the CM gapconfiguration information).

Alternatively, the carrier(s) selected for the measurement gaps may bepredetermined. For example, upon configuration of a measurement gap, theWTRU may apply the measurement gaps to a predetermined carrier, (e.g., asupplementary (or secondary) carrier(s)), keeping other UL and DLcarriers, (e.g., an anchor (or primary) carrier(s)), in fulltransmission and reception mode. The anchor (or primary) carrier may bedefined as a carrier that carries a specific set of control informationfor downlink/uplink transmissions. Any carrier that is not assigned asan anchor (or primary) carrier may be a supplementary (or secondary)carrier.

In case where multiple carriers may be selected for measurement gaps,the carriers may be determined based on a pre-defined pairing rule. Forexample, if two adjacent carriers are configured in two differentfrequency bands, respectively, (i.e., total four carriers areconfigured), the measurement gaps may be applied to all carriers withina specified frequency band, (e.g., the two adjacent carriers in one ofthe frequency bands in this example).

The WTRU may be indicated to start performing the inter-frequency and/orinter-RAT measurements on a particular carrier by disabling thatcarrier. Disabling of the carrier(s) may be indicated to the WTRU, forexample, via a high speed shared control channel (HS-SCCH) order orhigher layer signaling, (e.g., RRC message), or any type of signaling ormessage at any potocol layer. In case where a particular DL carrier(s)is disabled, the WTRU may stop reception on the disabled carrier(s) andperform inter-frequency and/or inter-RAT measurements using theavailable receiver which were used for the disabled carrier(s).

Embodiments for performing inter-frequency and/or inter-RAT measurementswhere at least one receiver of the multi-receiver WTRU is inactive areexplained hereafter. One example of this case is when a dual-banddual-cell HSDPA capable WTRU with two receivers is configured to operatewith single carrier HSDPA.

In accordance with one embodiment, no measurement gaps may be configuredfor the active receiver(s), and a WTRU may use the inactive receiver(s)to perform the inter-frequency and/or inter-RAT measurements. The WTRUmay perform the inter-frequency and/or inter-RAT measurementscontinuously using the inactive receiver. In this case, no measurementgaps may be configured for performing the inter-frequency and/orinter-RAT measurements.

Since the carrier activation and deactivation is controlled by theNode-B, (e.g., via physical layer signaling, such as HS-SCCH order), andthe measurement gaps are scheduled by the radio network controller (RNC)through an RRC message, the WTRU may receive the inter-frequency and/orinter-RAT measurement order from the RNC on the disabled carrier. Incase where a DL carrier has been disabled and the WTRU receives anindication with measurement gaps configuration to perform theinter-frequency and/or inter-RAT measurements on the disabled carrier,the WTRU may maintain the state of the carrier as “disabled” at aphysical layer (L1), and perform the inter-frequency and/or inter-RATmeasurements without any measurement gaps using the receiver which hadpreviously been associated with that carrier or any other availablereceiver (a receiver not assigned to an active channel).

If the disabled carrier is re-activated, (e.g., through L1 signalingsuch as an HS-SCCH order, or any other signaling or message), so thatall receivers become active, while the WTRU is scheduled to perform theinter-frequency and/or inter-RAT measurements on that disabled carrier,the WTRU may activate the DL reception and/or UL transmission on thatdisabled carrier(s), and may perform the inter-frequency and/orinter-RAT measurements in accordance with any one of the embodimentsdisclosed above for the case where all receivers are active.

In order to reduce the signalling load, the network may preset athreshold(s) and a timer(s) and configure events for starting andreporting the inter-frequency and/or inter-RAT measurements such that aWTRU may autonomously start and report the inter-frequency and/orinter-RAT measurements when at least one receiver is inactive. In thisembodiment, the WTRU may autonomously start the inter-frequency and/orinter-RAT measurements once the triggering condition(s) is met, and maynot inform the network about losing signal quality of the serving cellor the like in order to get an inter-frequency/inter-RAT measurementorder with or without measurement gaps, thus speeding up themeasurements order/reporting cycle.

FIGS. 5A and 5B is a flow diagram of an example process 500 forautonomous inter-frequency and/or inter-RAT measurements in accordancewith one embodiment. A WTRU determines whether there is at least oneinactive receiver (502). If so, the WTRU determines whether a triggercondition(s) is met (504). If either there is no inactive receiver orthe trigger condition(s) is not met, the WTRU may not perform theautonomous measurements (520). If there is at least one inactivereceiver and the trigger condition(s) is met, the WTRU may autonomouslystart the inter-frequency and/or inter-RAT measurements and report themeasurements to the network (506). If the WTRU receives an activationorder for a carrier(s) (508) and there is no inactive receiver (510),the WTRU may stop the autonomous inter-frequency/inter-RAT measurementson the activated carrier(s), activate the reception and/or ULtransmission on that carrier(s), and may perform the inter-frequencyand/or inter-RAT measurements in accordance with any one of theembodiments described above for the case where all receivers of the WTRUare active (512).

If there is additional inactive receiver (510), it is determined whetherthe additional inactive receiver is capable of working on that carrier(514). If the determination at 514 is positive, the WTRU may stop theautonomous inter-frequency and/or inter-RAT measurements on thatcarrier, activate the DL reception and/or UL transmission on thatcarrier, and configure and continue measurements without measurementgaps with the available inactive receiver if the trigger condition isstill met (516).

If the determination at 514 is negative, the WTRU may stop theautonomous inter-frequency and/or inter-RAT measurements and wait for ahigher layer configuration message for the measurement request withmeasurement gaps on the active carriers, and perform the inter-frequencyand/or inter-RAT measurements in accordance with any one of theembodiments disclosed above for the case that all receivers are active(518).

A home Node-B (HNB) or an evolved HNB (eHNB) may be deployed at customerpremises to off-load traffics from the macro Node-B and provide a betterlink quality and performance. An access to the HNB/eHNB is based on theHNB/eHNB cell identity, called closed subscriber group (CSG) identity(ID). For supporting mobility from the macro Node-B to the HNB or eHNB,a WTRU may send a proximity indication to the network when the WTRUdetects that it is near a HNB/eHNB cell whose CSG ID is in the listprovided by the network. The proximity indication may include the RATand the frequency of the detected HNB/eHNB cell. After receiving theproximity indication, the network, (e.g., radio network controller(RNC)), may configure measurement on the reported carrier or RAT tomeasure the HNB/eHNB cell. Measurement gaps, (e.g., CM gaps), may beactivated to allow the WTRU to perform the measurements on the reportedfrequency and RAT. The WTRU sends a measurement report to the network,and the network may configure the WTRU to perform system information(SI) acquisition and report SI. The WTRU may perform SI acquisitionusing autonomous gaps. The autonomous gaps are scheduled by the WTRU.The WTRU may suspend reception and transmission with the serving cell toacquire the relevant SI from the target HNB/eHNB.

In accordance with one embodiment, in case the WTRU is capable ofperforming an autonomous search for a Node-B, (e.g., an HNB or eHNBdetection), the inter-frequency and/or inter-RAT measurements may bestarted manually by the user. FIGS. 6A and 6B is a flow diagram of anexample process 600 for performing measurements in accordance with oneembodiment. A WTRU sends a proximity indication to the network when theWTRU detects that it is near a HNB/eHNB cell whose CSG ID is in theWTRU's list provided by the network (602). After sending the proximityindication to the Node-B, the WTRU may wait for gaps configuration fromthe network. If the autonomous gaps are supported and all receivers ofthe WTRU are active, the WTRU may perform the inter-frequency and/orinter-RAT measurements in accordance with any embodiments disclosedabove for the case where all the receivers of the WTRU are active whileconfiguring the autonomous gaps appropriately (604). If one or morereceivers are available, no measurement gaps may be required to startthe inter-frequency and/or inter-RAT measurements.

The WTRU receives an activation order for a carrier or a receiver whileperforming autonomously the inter-frequency and/or inter-RATmeasurements (606). It is determined whether the activation order is forthe receiver capable of working on a specific carrier/band, and whetherother inactive receivers are capable of working on that carrier/band(608).

If the determination at 608 is negative, it is further determinedwhether the autonomous gaps are supported (610). If it is determined soat step 610, the WTRU may stop the ongoing inter-frequency and/orinter-RAT measurements, activate the DL reception and/or UL transmissionfor the ordered carrier, send autonomously the proximity report in orderto get measurement gaps configuration from the network, and uponreceiving the gaps configuration, the WTRU may perform theinter-frequency and/or inter-RAT measurements based on any one of theembodiments disclosed above for the case where all receivers of the WTRUare active (612).

If the autonomous gaps are supported (610), the WTRU may stop theongoing inter-frequency and/or inter-RAT measurements, activate the DLreception and/or UL transmission for the ordered carrier, and configureautonomous gaps and continue the previous measurements using one of theremaining receiver(s) (614).

If the determination at 608 is positive, the WTRU may stop the ongoingmeasurements, activate the DL reception and/or UL transmission for theordered carrier, and continue measurements without gaps using one of theinactive receivers (616).

The WTRU may indicate to the network its multi-receiver capability,(e.g., capability of performing inter-frequency and/or inter-RATmeasurements while continuing transmission and reception on one or morecarriers). The WTRU may include a new capability information element ina higher layer signaling, (e.g., RRC message), to indicate the specificmulti-receive capability.

Alternatively, the network may infer that the WTRU has suchmulti-receiver capability from other capability indications of the WTRU.For example, the network may infer that all WTRUs indicating support ofdual-band dual-cell HSDPA are also capable of performing inter-frequencyand/or inter-RAT measurements while continuing transmission andreception on other carrier(s). Alternatively, a new WTRU-class may bedefined for WTRUs having the multi-receiver capability.

The multi-receiver capability may not be supported at all times by thenetwork, and the network may selectively activate and deactivate themulti-receiver capability of the WTRU. In accordance with oneembodiment, a WTRU may operate as required by the default mode, (e.g.,as required in the 3GPP Release 8), unless instructed otherwise by thenetwork. If the WTRU is instructed to operate with the multi-receivercapability by the network, the WTRU may operate in accordance with anyembodiment disclosed herein.

Alternatively, a new type of configuration command, (e.g., an RRCmessage), may be defined to configure the WTRU to operate in accordancewith any one of the embodiments disclosed herein such that once a WTRUreceives this new type of configuration command, the WTRU may performthe inter-frequency and/or inter-RAT measurements and related operationsin accordance with the embodiments disclosed herein. Alternatively, thenetwork may send an activation command, (e.g., via RRC message), toenable the WTRU to operate in accordance with the embodiments disclosedherein.

After handover to a target cell, the inter-frequency and/or inter-RATmeasurements and the related operations in accordance with anyembodiment disclosed herein may not be supported at the target cell. Inaccordance with one embodiment, the WTRU may revert to the default mode,(e.g., the operation in accordance with the 3GPP Release 8), until theWTRU is instructed otherwise. Alternatively, the handover command maycontain the necessary configuration information, and the WTRU mayconfigure itself as directed by the handover command. Alternatively, theWTRU may be network-aware and configure itself based on the capabilitiesof the serving Node-B.

Although features and elements are described above in particularcombinations, one of ordinary skill in the art will appreciate that eachfeature or element can be used alone or in any combination with theother features and elements. In addition, the methods described hereinmay be implemented in a computer program, software, or firmwareincorporated in a computer-readable medium for execution by a computeror processor. Examples of computer-readable media include electronicsignals (transmitted over wired or wireless connections) andcomputer-readable storage media. Examples of computer-readable storagemedia include, but are not limited to, a read only memory (ROM), arandom access memory (RAM), a register, cache memory, semiconductormemory devices, magnetic media such as internal hard disks and removabledisks, magneto-optical media, and optical media such as CD-ROM disks,and digital versatile disks (DVDs). A processor in association withsoftware may be used to implement a radio frequency transceiver for usein a WTRU, UE, terminal, base station, RNC, or any host computer.

1. A method implemented in a multi-receiver wireless transmit/receiveunit (WTRU) for performing inter-frequency and/or inter-radio accesstechnology (RAT) measurements, the method comprising: determiningwhether to use either an inactive receiver or measurement gaps forinter-frequency and/or inter-RAT measurements based on an activationstatus of carriers at a physical layer; and performing inter-frequencyand/or inter-RAT measurements using either an inactive receiver ormeasurement gaps based on the determination.
 2. The method of claim 1wherein the inter-frequency and/or inter-RAT measurements are performedusing an inactive receiver without configuring measurement gaps on acondition that at least one inactive receiver is available.
 3. Themethod of claim 2 wherein the inter-frequency and/or inter-RATmeasurements are scheduled autonomously by the WTRU.
 4. The method ofclaim 1 further comprising: receiving a measurement order on a disabledcarrier, wherein the inter-frequency and/or inter-RAT measurements areperformed using an inactive receiver on the disabled carrier withoutmeasurement gaps while maintaining a status of the disabled carrier asdisabled at the physical layer.
 5. The method of claim 1 wherein theinter-frequency and/or inter-RAT measurements are performed usingmeasurement gaps on a condition that there is no inactive receiveravailable.
 6. The method of claim 5 wherein the measurement gaps areconfigured on a downlink carrier and not on an uplink carrier.
 7. Themethod of claim 5 wherein the measurement gaps are configured on anunpaired downlink carrier and not on a paired downlink carrier.
 8. Themethod of claim 5 wherein the measurement gaps are configured on asubset of associated downlink-uplink carrier pairs.
 9. The method ofclaim 1 further comprising: determining whether a trigger condition forthe inter-frequency and/or inter-RAT measurements is met, wherein theinter-frequency and/or inter-RAT measurements are performed on acondition that the trigger condition is met.
 10. The method of claim 1further comprising: detecting a home Node-B (HNB) cell or a home evolvedHNB (eHNB) cell; sending a proximity indication on a condition that anidentity of the detected HNB or eHNB cell is in a list that the WTRUreceived from a network; and performing the inter-frequency and/orinter-RAT measurements on a frequency carrier or an RAT of the detectedHNB or eHNB cell.
 11. A multi-receiver wireless transmit/receive unit(WTRU) for performing inter-frequency and/or inter-radio accesstechnology (RAT) measurements, the WTRU comprising: a receiverconfigured to receive via at least two downlink carriers simultaneously;and a processor configured to determine whether to use either aninactive receiver or measurement gaps for inter-frequency and/orinter-RAT measurements based on an activation status of carriers at aphysical layer, and perform inter-frequency and/or inter-RATmeasurements using either an inactive receiver or measurement gaps basedon the determination.
 12. The WTRU of claim 11 wherein the processor isconfigured to perform the inter-frequency and/or inter-RAT measurementsusing an inactive receiver without configuring measurement gaps on acondition that at least one inactive receiver is available.
 13. The WTRUof claim 12 wherein the processor is configured to schedule theinter-frequency and/or inter-RAT measurements autonomously.
 14. The WTRUof claim 11 wherein the processor is configured to receive a measurementorder on a disabled carrier, and perform the inter-frequency and/orinter-RAT measurements using an inactive receiver on the disabledcarrier without measurement gaps while maintaining a status of thedisabled carrier as disabled at the physical layer.
 15. The WTRU ofclaim 11 wherein the processor is configured to perform theinter-frequency and/or inter-RAT measurements using measurement gaps ona condition that there is no inactive receiver available.
 16. The WTRUof claim 15 wherein the measurement gaps are configured on a downlinkcarrier and not on an uplink carrier.
 17. The WTRU of claim 15 whereinthe measurement gaps are configured on an unpaired downlink carrier andnot on a paired downlink carrier.
 18. The WTRU of claim 15 wherein themeasurement gaps are configured on a subset of associated downlinkuplink carrier pairs.
 19. The WTRU of claim 11 wherein the processor isconfigured to determine whether a trigger condition for theinter-frequency and/or inter-RAT measurements is met, and perform theinter-frequency and/or inter-RAT measurements on a condition that thetrigger condition is met.
 20. The WTRU of claim 11 wherein the processoris configured to detect a home Node-B (HNB) cell or a home evolved HNB(eHNB) cell, send a proximity indication on a condition that an identityof the detected HNB or eHNB cell is in a list that the WTRU receivedfrom a network, and perform the inter-frequency and/or inter-RATmeasurements on a frequency carrier or an RAT of the detected HNB oreHNB cell.